/*
*      crc16.c
*
* This source code is licensed under the GNU General Public License,
* Version 2. See the file COPYING for more details.
*/

#include <crc16.h>


#ifndef CRC16_LOOKUP_TABLE
#define CRC16_LOOKUP_TABLE	0
#endif


#if	(CRC16_LOOKUP_TABLE)

#include <avr/pgmspace.h>
#define CRC16_TABLE(shift) 	(pgm_read_word(crc16_table + (shift)) & 0xFFFF)

/** CRC table for the CRC-16. The poly is 0x1021 (x^16 + x^12 + x^5 + 1) */
//const unsigned short crc16_table[256] = {
static prog_uint16_t crc16_table[256] = {
	0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50a5, 0x60c6, 0x70e7, 
	0x8108, 0x9129, 0xa14a, 0xb16b, 0xc18c, 0xd1ad, 0xe1ce, 0xf1ef, 
	0x1231, 0x0210, 0x3273, 0x2252, 0x52b5, 0x4294, 0x72f7, 0x62d6, 
	0x9339, 0x8318, 0xb37b, 0xa35a, 0xd3bd, 0xc39c, 0xf3ff, 0xe3de, 
	0x2462, 0x3443, 0x0420, 0x1401, 0x64e6, 0x74c7, 0x44a4, 0x5485,
	0xa56a, 0xb54b, 0x8528, 0x9509, 0xe5ee, 0xf5cf, 0xc5ac, 0xd58d, 
	0x3653, 0x2672, 0x1611, 0x0630, 0x76d7, 0x66f6, 0x5695, 0x46b4, 
	0xb75b, 0xa77a, 0x9719, 0x8738, 0xf7df, 0xe7fe, 0xd79d, 0xc7bc, 
	0x48c4, 0x58e5, 0x6886, 0x78a7, 0x0840, 0x1861, 0x2802, 0x3823, 
	0xc9cc, 0xd9ed, 0xe98e, 0xf9af, 0x8948, 0x9969, 0xa90a, 0xb92b, 
	0x5af5, 0x4ad4, 0x7ab7, 0x6a96, 0x1a71, 0x0a50, 0x3a33, 0x2a12, 
	0xdbfd, 0xcbdc, 0xfbbf, 0xeb9e, 0x9b79, 0x8b58, 0xbb3b, 0xab1a, 
	0x6ca6, 0x7c87, 0x4ce4, 0x5cc5, 0x2c22, 0x3c03, 0x0c60, 0x1c41, 
	0xedae, 0xfd8f, 0xcdec, 0xddcd, 0xad2a, 0xbd0b, 0x8d68, 0x9d49, 
	0x7e97, 0x6eb6, 0x5ed5, 0x4ef4, 0x3e13, 0x2e32, 0x1e51, 0x0e70, 
	0xff9f, 0xefbe, 0xdfdd, 0xcffc, 0xbf1b, 0xaf3a, 0x9f59, 0x8f78, 
	0x9188, 0x81a9, 0xb1ca, 0xa1eb, 0xd10c, 0xc12d, 0xf14e, 0xe16f, 
	0x1080, 0x00a1, 0x30c2, 0x20e3, 0x5004, 0x4025, 0x7046, 0x6067, 
	0x83b9, 0x9398, 0xa3fb, 0xb3da, 0xc33d, 0xd31c, 0xe37f, 0xf35e, 
	0x02b1, 0x1290, 0x22f3, 0x32d2, 0x4235, 0x5214, 0x6277, 0x7256, 
	0xb5ea, 0xa5cb, 0x95a8, 0x8589, 0xf56e, 0xe54f, 0xd52c, 0xc50d, 
	0x34e2, 0x24c3, 0x14a0, 0x0481, 0x7466, 0x6447, 0x5424, 0x4405,
	0xa7db, 0xb7fa, 0x8799, 0x97b8, 0xe75f, 0xf77e, 0xc71d, 0xd73c, 
	0x26d3, 0x36f2, 0x0691, 0x16b0, 0x6657, 0x7676, 0x4615, 0x5634, 
	0xd94c, 0xc96d, 0xf90e, 0xe92f, 0x99c8, 0x89e9, 0xb98a, 0xa9ab, 
	0x5844, 0x4865, 0x7806, 0x6827, 0x18c0, 0x08e1, 0x3882, 0x28a3, 
	0xcb7d, 0xdb5c, 0xeb3f, 0xfb1e, 0x8bf9, 0x9bd8, 0xabbb, 0xbb9a, 
	0x4a75, 0x5a54, 0x6a37, 0x7a16, 0x0af1, 0x1ad0, 0x2ab3, 0x3a92, 
	0xfd2e, 0xed0f, 0xdd6c, 0xcd4d, 0xbdaa, 0xad8b, 0x9de8, 0x8dc9, 
	0x7c26, 0x6c07, 0x5c64, 0x4c45, 0x3ca2, 0x2c83, 0x1ce0, 0x0cc1, 
	0xef1f, 0xff3e, 0xcf5d, 0xdf7c, 0xaf9b, 0xbfba, 0x8fd9, 0x9ff8, 
	0x6e17, 0x7e36, 0x4e55, 0x5e74, 0x2e93, 0x3eb2, 0x0ed1, 0x1ef0,
};

unsigned int crc16(unsigned int crc, char *buffer, int len) {
    unsigned int  i;
    unsigned int crcvalue = crc;
	unsigned int cache;

    for (i = 0; i < len; i ++) {
		cache = CRC16_TABLE(( crcvalue >> 8 ) ^ *buffer++);
        crcvalue = ( crcvalue << 8 ) ^ cache;
	}
    return crcvalue;
}

#endif // if (CRC16_LOOKUP_TABLE)

#if (0)
unsigned short crc16_byte(unsigned short crc, const char data) {
	return (crc >> 8) ^ crc16_table[(crc ^ data) & 0xff];
}

/*
* crc16 - compute the CRC-16 for the data buffer
* @crc:        previous CRC value
* @buffer:     data pointer
* @len:        number of bytes in the buffer
*
* Returns the updated CRC value.
*/
unsigned short crc16(unsigned short crc, unsigned char *buffer, unsigned int len) {
	while(len--) {
		crc = crc16_byte(crc, *buffer++);
	}
	return crc;
}
#endif


#if (1)
unsigned int _crc16(unsigned int crc, unsigned char *buffer, unsigned int len) {
	unsigned int i, j;
	unsigned long lcrc = crc;
	
	for(i = 0;i < len; i ++){
		for(j = 0;j < 8; j++){
			lcrc <<= 1;
			if(((*(buffer+i) << j) & 0x80) == 0x80){
				lcrc |= 0x01;
			}
			if((lcrc & 0x10000) == 0x10000){     	 
				lcrc ^= 0x1021;
			}			
	    }
	}
	for(i = 0;i < 16;i ++){
		lcrc <<= 1;
	    if((lcrc & 0x10000) == 0x10000) 
			lcrc ^= 0x1021;
	}
	return lcrc & 0xffff;
}


void crc16_hook(int x) {


	if(CRC16_TABLE(1) == 0x1021)
		usart_output_str("fuck it");
	else
		usart_output_str("get fucked");
	//usart_output_hex((unsigned short)CRC16_TABLE(x));
}

#endif




